(1) Field of the Invention
The invention relates to the fabrication of integrated circuit devices, and more particularly, to a method of improving the quality and uniformity of a selective TiSi.sub.2 deposition in the fabrication of integrated circuits.
(2) Description of the Prior Art
It is well known that it is very difficult to form a high quality uniform TiSi.sub.2 film on narrow polysilicon lines, especially in deep sub-micron devices. One of the methods that has been used to overcome this technology barrier is to selectively deposit TiSi.sub.2 onto the polysilicon and active silicon areas. The advantage of this approach is that there is no consumption of silicon at the source/drain regions.
Although selective CVD TiSi.sub.2 is a promising technique, it has been found that the localized deposition rate is a strong function of the quality of the polysilicon and silicon surfaces--cleanliness, damage, etc. FIG. 1 illustrates a typical example of the effects that polysilicon etch damage on the sidewalls of the polysilicon line can have on the CVD TiSi.sub.2 deposition. A polysilicon line 16 is shown on the surface of a semiconductor substrate 10. TiSi.sub.2 21 has been selectively deposited on the top surface of the polysilicon line. It can be seen that excess TiSi.sub.2 23 deposited at the edges of the polysilicon line due to polysilicon sidewall roughness. In practice, an insulating spacer will be formed on the sidewalls of the polysilicon line. However, the top portion of the spacers is etched away by wet chemicals leaving the top corners of the polysilicon line exposed. The roughness of the top corners of the lines causes the excess TiSi.sub.2 deposition at the edges of the polysilicon lines.
U.S. Pat. No. 5,023,201 to Stanasolovich et al teaches forming a TiSi.sub.2 layer on the substrate and the n selectively depositing tungsten overlying the TiSi.sub.2 and annealing to transform the TiSi.sub.2 to the C54 phase. The process of Stanasolovich et al is not adequate for deep sub-micron polysilicon lines. U.S. Pat. No. 5,672,544 to Pan, U.S. Pat. No. 5,668,024 to Tsai et al, U.S. Pat. No. 5,593,924 to Apte et al, and U.S. Pat. No. 4,933,994 to Orban show other salicide processes using TiSi.sub.2.